Steven Universe - Basically: the origin

Also, I know that it's not the same demographic, but…

But of course there's also nothing wrong with shows that lean more in one direction over another so long as it does it well.

For example in the realm of a show that focuses more on comedy over seriousness The Amazing World of Gumball is great at what it does with its brand of slapstick and comedic writing (for example the last 1/4 of the episode "The Check" focuses on an "invisible car" chase worthy of Fast and the Furious that was amazing). Another good example would be most anything Looney Tunes related, doesn't matter if it's the older slapstick of the "golden age" cartoons or the more sitcom-like Looney Tunes Show, they all focused on what silly situations the characters got themselves into and did it well.

On the other end of the spectrum, Cowboy Bebop and Michiko and Hatchin are two shows that are most definitely more serious than comedic, and they do it well with how they do things like portray character relationships and serious topics in spite of the fact both are fictional cartoons.